RCD tripping while Zs

[nicsin02]

Hi guys, what would cause an RCD to trip when carrying out a Zs test, it is a lighting circuit in a new build house and I have it on the "no trip" setting and it still trips the RCD, the RCD itself passed the RCD tests and the IR is 800Mohms so that's fine, I even even replaced the RCD but the problem still exits, just a note it is a dual RCD board with each RCD protecting 4 mcb's and all other Zs test are fine its just the lighting circuit, any ideas guys, thanks in advance

 

[ste77]

"no trip" unfortunately doesnt mean what it says. certain rcds and test meters are incompatible for rcd testing on any scale.

 

[Sintra]

What make of meter are you using?

 

[nicsin02]

It wasn't actually myself doing the testing it was the tester from my old company that fned me to see if I had any ideas, it is a robin ELI tester, he has been using it for years and he tested a few properties after the above mentioned and everything was fine so I don't think the tester is a fault

 

[chrish_1977]

I have had that happen a few times with my megger, ha all three probes on their corresponding conductors, but it only ever did it on lighting circuits.

 

[MDJ]

is the non trip test on your meter jut 2 wire, some older meters have to have three leads for the non trip test.

 

[MarkieSparkie]

It wasn't actually myself doing the testing it was the tester from my old company that fned me to see if I had any ideas, it is a robin ELI tester, he has been using it for years and he tested a few properties after the above mentioned and everything was fine so I don't think the tester is a fault

If the guy was using a Robin yellow brick with D-lok (eg. KMP4120) it will not trip most passive RCDs, but the DC blocking method of 'No-trip' that the Robin uses is likely to be ineffective and trip a lot of modern sensitive RCDs, most RCBOs fall in to this later group.

 

[telectrix]

inb this case, the answer is to bridge out the RCD for testing. don't forget to remove the links after.

 

[wildgoose]

If everything else is ok, then generate your ZS value through calculation
ZS=ZE + (R1+R2)

Calculation is encouraged as an alternative to live measurements!

 

[telectrix]

If everything else is ok, then generate your ZS value through calculation
ZS=ZE + (R1+R2)

Calculation is encouraged as an alternative to live measurements!

for wimps.

 

[wildgoose]

Don't tell me that an old soldier like you hasn't forgot to measure it and thought "sod it, I'll get the value by calc"

 

[telectrix]

i usually guess it anyway. NOT. :wink_smile:

 

[diditrain]

Were there other circuit`s sharing the RCD, and were they energised at the time of testing?

 

[rmc86uk]

We had the exact same problem today doing a Zs test kept tripping the circuit breakers in the control panel. Some of the breakers were 2A and 4A when tried with a higher breaker it wouldn't trip.

Sent from my GT-I9300 using Tapatalk 2

 

[Edd]

If your doing a 2 wire Zs test and the RCD trips try swoping the leads over so E on line and L on Earth. That was megger's answer and it works.